Abstract: An association complex formed between coordination complex of Fe(Ⅱ)-o-phenanthroline and γ-aminobutyric acid was prepared and used as electroactive material in the preparation of γ-aminobutyric acid modified carbon paste electrode, and the electrochemical properties of this modified electrode were studied. Good response of this electrode against γ-aminobutyric acid was obtained giving linearity range from 1.0×10-5 to 8.0×10-2mol·L-1, with a slope of 38 mV·pc-1 and lower limit of determination (10S/N) of 5.2×10-6mol·L-1. The modified electrode was used in the potentiometric determination of γ-aminobutyric acid in sample of brown rice, highland barly and green tea, the results obtained were checked quite well with those found by spectrophotometry.